The Islamic State of Iraq and Syria, or ISIS, attacked an air base in Iraq that houses U.S. military personnel, the Pentagon said Saturday.

The Pentagon said no service members in the coalition fighting ISIS were affected by the attack at the Ayn al-Assad Air Base.

Citing Iraqi officials, a U.S. military official said that between three and four fighters wearing explosive vests were killed in the attack, CBS Radio News correspondent Cami McCormick reports.

The official said there were no casualties in the attack, McCormick reports.